Abstract

Most animals look at each other to signal threat or interest.
In humans, this social interaction is usually punctuated
with brief periods of mutual eye contact. Deviations from
this pattern of gazing behaviour generally make us feel
uncomfortable and are a defining characteristic of clinical
conditions such as autism or schizophrenia, yet it is unclear
what constitutes normal eye contact. Here, we measured, across
a wide range of ages, cultures and personality types, the
period of direct gaze that feels comfortable and examined
whether autonomic factors linked to arousal were indicative
of people’s preferred amount of eye contact. Surprisingly, we
find that preferred period of gaze duration is not dependent on
fundamental characteristics such as gender, personality traits
or attractiveness. However, we do find that subtle pupillary
changes, indicative of physiological arousal, correlate with the
amount of eye contact people find comfortable. Specifically,
people preferring longer durations of eye contact display faster
increases in pupil size when viewing another person than
those preferring shorter durations. These results reveal that
a person’s preferred duration of eye contact is signalled by
physiological indices (pupil dilation) beyond volitional control
that may play a modulatory role in gaze behaviour.